There is always a risk that, e.g., a dishwasher and/or a washing machine overflows. If this happens when the owner is not at home, the entire home can be flooded resulting in enormous damages. Other appliances that could overflow are, e.g., an oil boiler or a water softening plant. Thus, such problems are encountered not only by house owners and landlords, but also by manufacturers and business owners.
Insurance companies are very strict in their disbursements and the insured party must usually be able to show all due care. Thus, if the insured party would like to run the appliance unguarded, it could result in a very costly experience.